WI - Cormorant Research Group The Bulletin - No. 3, December 1998 Original papers

Summary of an international meeting of experts to complete "The development of an action plan for the Great Cormorant in the African-Eurasian Region".

A meeting was held at Copenhagen on 25 and 26 September 1997 concerning the elaboration of an action plan for the Great Cormorant in the African-Eurasian region. This meeting is a following step of § 5.3 of the recommendation from the Conference of the Parties of the Bonn Convention, in which Denmark and the Netherlands are invited to take the necessary steps, involving all interested Range States, to bring together an international group of experts from the nature conservation and fisheries sectors, to complete the action plan mentioned in the recommendations. The aim of the meeting, presided by Dr Pierre Devillers, is to discuss the Action plan and to advise Denmark and the Netherlands with the completion.

After a welcoming word by Mr Ole Andersen from guest country Denmark, the agenda was agreed upon. In this respect, an introduction of the backgrounds for the meeting was provided by the president. Both the expert group and the president are supposed to form a group of independent experts. After some questions concerning the next steps, it is agreed that Denmark and the Netherlands will finish the Action Plan before the end of 1997 and send it to all other participating countries and to the Scientific Council according to § 4 of the Recommendation. Afterwards both countries will consider their task to be finished. The actual implementation of the plan is foreseen for the future.

The Management Guidelines have been discussed. The list of measures was adapted and together with a new introductory paragraph included in the final version of the Action Plan. Denmark and the Netherlands, specifically mentioned in the Recommendations, presented "a possible procedure for the Advisory Committee" and asked the "expert group" to comment upon it. Formally, the expert group is only allowed to make recommendations and not to decide on a procedure for the advisory committee.

With respect to contents, it is decided to leave out the announcement of future measurements, as they are unrealistic. It was the general opinion that the aims and objectives of the Action Plan for the management of the Great Cormorant in the African-Eurasian region needed revision. A proposal by Germany to include an advice for the reduction of Great Cormorant numbers was rejected, only being supported by the representative of the EIFAC. The majority of the meeting was of the opinion that reduction of the overall population cannot be the objective of the action plan and that the singling out of a single measure is not appropriate. Such a passage was removed earlier as well at the Geneva meeting. A proposal prepared by the UK was, slightly adapted, incorporated into the final version of the plan. This new text is as follows: "The aim of the plan is to minimise the conflict between fisheries interests and the Great Cormorant Phalacrocorax carbo sinensis by ensuring that best practise is followed in mitigating, preventing and reducing the reported impacts of the species on fisheries, while maintaining a favourable conservation status for the species. Range states should try to achieve this, in the following order of preference through:

No countries were prepared to volunteer and take over the lead from Denmark and the Netherlands to bring up the document further. Denmark and the Netherlands will make the final version and suggest that candidate states wishing to take the lead should contact the Bonn Convention Secretariat.

For Germany the Action Plan is not acceptable since it is not sufficient to reduce the conflicts between cormorants and fisheries in Germany. As the plan strongly differs from the expectations by EIFAC, for them too the plan turned out to be very disappointing.

The conclusions of the expert meeting were:

Range States are encouraged to implement immediately the proposals outlined in the Action Plan.


RECENT PUBLICATIONS ON CORMORANTS

During 1997 two important PhD theses on European cormorants have been published by our German colleagues. In March 1997 Thomas Keller produced his "Qualitative und quantitative Untersuchungen zur Nahrungsökologie in Bayern überwinternder Kormorane (Phalacrocorax carbo sinensis)" (Keller 1997), written in German but with extensive English summaries and figure captions. After a short introduction on taxonomy and biology of the species and a summary of its distribution and recent population developments in Europe, the author focuses on a qualitative and quantitative diet study carried out in Bavaria, southern Germany. This study was initiated out of concern about the impact on fish and fisheries of the increasing wintering numbers of Great Cormorants from breeding colonies in North-western Europe on alpine and subalpine lakes, rivers and reservoirs. Almost 3000 regurgitate pellets were collected for diet analysis in this study and a further 2000 pellets from an earlier study were included as well. Almost 10,000 individual prey items were identified, among which cyprinid fish were predominant on all seven different roost sites. Furthermore, on two large pre-alpine lakes a significant proportion of the birds’ diet consisted of whitefish Coregonus spp., while locally (both on lakes and on rivers) percid fish were important as well. On one fast-flowing river salmonid fish was frequently taken and on one lake Eel Anguilla anguilla made up an important proportion of the prey items. Assuming a production of one regurgitate pellet per bird per day, the back-calculation of fish mass per pellet based on sizes of undigestable fish remains suggested an increase in daily food intake throughout the winter, followed by a steady decrease in the subsequent summer months. Intake peaks were reached in April/May. Daily energy expenditure (DEE) was measured by the doubly labelled water technique, applied to both caged birds and free-ranging individuals. Estimated DEE ranged from an average of 1263 kJ day-1 in the captive birds to an average of 2025 kJ day-1 in the field. This difference was shown to be statistically significant and was unlikely to be caused by differences in average body mass between the two groups. Daily food needs to meet the measured DEE values were calculated at 325 g of fish for the zoo cormorants and at 521 g for the free-living birds.

The same month of March 1997 David Grémillet also published his PhD thesis, entitled: "Wettable gluttons of the sea? The foraging ecology of breeding Great Cormorants (Phalacrocorax carbo, L.) and European Shags (Phalacrocorax aristotelis, L.)" (Grémillet 1997). Qualitative diet composition of marine-breeding Great Cormorants and European Shags from the Chausey Islands (France) was examined on the basis of 526 regurgitate pellets (containing 13,016 otoliths) and 353 regurgitated fish. Moreover, individual birds of both species have been equipped withVHF-transmitters, a radio-tracking system and time-depth-recorders. Thus, their favourite foraging grounds were located as well as details on timing and way of diving. The author states that Great Cormorants are rather more flexible foragers than European Shags, the latter probably just accommodating its feeding and diving patterns to variations in the availability of its main prey sandeels Ammodytidae. For Great Cormorants it is demonstrated that ‘benthic’ dives are about as frequent as ‘pelagic’ dives and that individual birds may dive deeper (down to 32 m) and longer (up to 152 s) than previously thought. Moreover, different birds were found to favour different depth zones, thus suggesting that individually specialised diving techniques strongly determine individual foraging strategies (and therefore also prey choice). This was corroborated by the results from individual radio-tracking, which showed a high degree of fidelity to certain foraging areas. Foraging efficiency, as measured by the use of automatic nest balances combined with radio-tracking data, turned out to be very high compared to other seabirds or marine mammals: 15.2 g of fish were taken per minute spent under water in males and 9.0 g min-1 in females. Increasing food needs of the chicks were met by carrying out more daily feeding trips, thus increasing overall foraging effort. This, however, was shown to have no negative impact on adult body mass. Finally, a rough calculation was made of the total food intake of Great Cormorants and European Shags breeding on Chausey in 1995. This estimate amounted to about 98 tonnes of fish, of which just 68% is of commercial value. Thus, only 1.6% of the total amount of fish landed by fishermen over the same period was taken by the birds.

Keller, T. 1997. Qualitative und quantitative Untersuchungen zur Nahrungsökologie in Bayern überwinternder Kormorane (Phalacrocorax carbo sinensis). Den Naturwissentschaftlichen Fakultäten der Friedrich-Alexander-Universität Erlangen-Nürnberg.

Grémillet, D. 1997. Wettable gluttons of the sea? The foraging ecology of breeding Great Cormorants (Phalacrocorax carbo, L.) and European Shags (Phalacrocorax aristotelis, L.). Mathematisch-Naturwissentschaftliche Fakultät der Christian-Albrechts-Universität zu Kiel.


REQUESTS FOR INFORMATION

Request for photographs of races of Great Cormorant in Europe

Stuart Newson is presently carrying out a study on productivity of Great Cormorants for a research MSc at the University of Bristol in collaboration with the Wildfowl and Wetlands Trust, Slimbridge. His aims are to compare breeding phenology and productivity between inland and coastal colonies throughout the British Isles and to identify factors affecting productivity.

Whilst carrying out his work, he has become particularly interested in determining the validity of using morphological characteristics in the field to determine geographical origins of individuals. In view of recent developments on ‘Fuzzy Neural Net’ (a form of artificial intelligence) being used to differentiate different colony forming units of Viridae, he found it might be interesting to see what features this method would pinpoint as being diagnostic of the two races, sinensis and carbo.

Now, Stuart Newson is in need for photos, or clear black and white photocopies of photos, of individual Great Cormorants recently dead or alive, showing a side-on view of the head with the beak horizontal and shut. These birds may be of any age or sex, but the pictures should preferably be taken of birds during the breeding season and from known colonies.

All contributors will of course be fully acknowledged for anything that is published as a result of this work and none of the photos or photocopies will appear in print. Can you help him out? Please do not hesitate in contacting:

Stuart Newson, The Wildfowl & Wetlands Trust, Slimbridge, Glos GL2 7 BT, United Kingdom


Need for an update of colour-ringing programmes on Great Cormorants in Europe

In order to achieve a better correspondence and understanding between ring-readers and administrators of ringing data we have decided to make an update of colour-ringing work on Great Cormorants. In the nineties several new programmes have been started, resulting in the use of new colours and different codes. More and more, regular cormorant observers are getting confused about whom to contact about their observations of individually marked birds. In the table given below all colour-ringing work in the Netherlands is summarised. Hopefully everyone managing a colour-ringing programme on Great Cormorants will be able to provide us with a similar table. We shall then be able to publish it in the next CRG-Bulletin and to send it to everyone requiring more information about the subject.

colour period leg inscr. code
yellow 1983-1995 right black 2 letter number or combination (bars)
white 1983-1995 left black 2 letter number or combination (bars)
green 1993- right white 2 letters with bar
red 1996- left white 2 letter number or combination (bars)
green 1997- left white number letter or letter number (bars)

You may send your information to, or ask for more of our information, from:

Stef van Rijn, Rijkswaterstaat RIZA, P.O. Box 17, NL-8200 AA Lelystad, The Netherland